[Technical Field ]
The present disclosure relates to a method and apparatus for correcting motions of a robot, and in particular, to a method and apparatus for correcting changes in motions of industrial robots due to mechanical deflection developed in the robot.
[Related Art ]
Industrial robots nowadays are indispensable production means in factories and other facilities. These industrial robots (simply termed robot(s) hereinafter) are generally used, with a tool suitable for the usage being attached to the end effector. Such a robot may make a motion applying a force in a direction perpendicular to its installation surface, such as when assembling a workpiece held by the tool to a predetermined position of an object, or when screwing a screw to a workpiece if the tool is a screwdriver or the like.
When making such a motion, the force to be generated by the robot is usually acquired by a sensor or the like, and controlled in terms of impedance, for example, so that the acquired force will be a specified pressing force. To prevent scratches on the surface of the workpiece or to prevent damage to the workpiece when applying the force, the tip end of the tool is required to be aligned over the object with high accuracy, and the load torque is required to be estimated with high accuracy.
However, the fact is that accurate alignment made under control may be lost due to mechanical deflection of the robot which is caused by its own weight or the like. In the occurrence of mechanical deflection, the tip end position of the tool may be misaligned from the target position, disabling assemblage of the workpiece, or the load torque may be erroneously estimated, leading to application of an excessively large force. As measures against such mechanical deflection, a patent document JP H04-233602 A proposes detecting the mechanical deflection caused in a robot and correcting the end effector position of the robot.